Subscriber in a bus system, method for operation and a bus system

Abstract

A bus system, a method for operating a bus system and a participant of a bus system are provided. The participant includes a timer and a transceiver circuit. The transceiver circuit is configured to receive a data packet having a time stamp value via a bus. The timer is configured for synchronization, based on the time stamp value. The timer is configured to change the time stamp value. The transceiver circuit is configured to transmit the data packet with the changed time stamp value via the bus.

What is claimed is: 
     
       1. A participant of a bus system comprising:
 a timer; 
 a transceiver circuit configured to receive a data packet having a time stamp value via a bus; 
 wherein the timer is configured for synchronization, based on the time stamp value, 
 wherein the timer is configured to change the time stamp value to a changed time stamp value, 
 wherein the transceiver circuit is configured to transmit the same data packet with the changed time stamp value via the bus, 
 wherein the data packet includes data symbols each having a fixed number of bits, wherein a plurality of the data symbols comprise the time stamp value of the data packet, and wherein the transceiver circuit is configured to receive and to transmit the data packet data symbol by data symbol such that a transmission of one of the data symbols of the data packet and a receipt of a subsequent one of the data symbols of the data packet takes place simultaneously, and 
 wherein the transceiver circuit is configured to change a data symbol of the time stamp value that is received first and has a least significant bit of the time stamp value and transmit the data symbol having the least significant bit to a subsequent participant before receiving a data symbol of the time stamp value having a most significant bit of the time stamp value. 
 
     
     
       2. The participant according to  claim 1 , wherein the timer includes a time counter, and wherein the timer includes a state machine which is configured to synchronize the time counter based on the time stamp value and to change the time stamp value to the changed time stamp value. 
     
     
       3. The participant according to  claim 1 , further comprising a non-volatile memory area for storing a correction value, on which the change of the time stamp value is based. 
     
     
       4. The participant according to  claim 3 , wherein the correction value is based on a delay between the receipt and the transmission of a beginning of the data packet by the transceiver circuit and based on a delay due to the transmission via a transmission path of the bus to a subsequent participant. 
     
     
       5. The participant according to  claim 3 , wherein the correction value is constant for consecutive data packets. 
     
     
       6. A method for operating a bus system, the method comprising:
 providing a first participant; 
 providing a second participant; 
 receiving and transmitting a data packet by the first participant; 
 synchronizing a timer of the first participant based on a time stamp value received in the data packet; 
 changing the time stamp value to a changed time stamp value by the first participant; and 
 transmitting the changed time stamp value by the first participant to the second participant via the same data packet, 
 wherein the bus system has a first interface device, the first participant being removable from the bus system by detaching the first participant from the first interface device, and 
 wherein the first interface device includes a first switching device which effectuates a bypass to the second participant so that the data packet is receivable not by the first participant but rather by the second participant with an unchanged time stamp value if the first participant is removed. 
 
     
     
       7. The method according to  claim 6 , wherein the time stamp value is changed by the first participant during the transmission and the receipt of the data packet. 
     
     
       8. The method according to  claim 6 , wherein a propagation time delay caused by the first participant is ascertained prior to the receipt of the data packet, wherein a correction value is ascertained based on the propagation time delay, wherein the correction value is stored, and wherein the change of the time stamp value is based on the correction value. 
     
     
       9. The method according to  claim 8 , wherein a further propagation time delay caused by a transmission path between the first participant and the second participant is ascertained prior to the receipt of the data packet, and wherein the correction value is ascertained based on the propagation time delay and the further propagation time delay. 
     
     
       10. The method according to  claim 9 , wherein the changed time stamp value is determined by summing the time stamp value and the correction value. 
     
     
       11. A bus system comprising:
 a first participant configured as a first slave; 
 a second participant configured as a second slave; 
 a master; 
 a bus; and 
 a first interface device, wherein the first slave is removable from the bus system by detaching the first slave from the first interface device, 
 wherein the master and the first slave and the second slave are connected via the bus to transmit a data packet such that the data packet transmitted by the master passes through the first slave and the second slave in a fixed sequence, 
 wherein the master is configured to transmit a time stamp value in the data packet, 
 wherein the first slave is configured to receive the data packet with the time stamp value, 
 wherein the first slave is configured to synchronize a timer of the first slave based on the time stamp value, 
 wherein the first slave is configured to change the time stamp value to a changed time stamp value and to transmit the changed time stamp value to the second slave in the data packet, 
 wherein the second slave is configured to receive the data packet with the changed time stamp value and to synchronize a timer of the second slave based on the changed time stamp value, and 
 wherein the first interface device includes a first switching device which effectuates a bypass to the second slave so that the data packet is receivable not by the first slave but rather by the second slave with an unchanged time stamp value if the first slave is removed. 
 
     
     
       12. The bus system according to  claim 11 , further comprising:
 at least two additional slaves, 
 wherein the data packet passes through all of the at least two additional slaves of the bus system in a fixed sequence, 
 wherein each slave is configured to successively change the time stamp value in the data packet and to forward the data packet to the subsequent slave in the sequence via the bus, 
 wherein the last slave in the sequence is configured to transmit the data packet back to the master via the bus. 
 
     
     
       13. The bus system according to  claim 11 , wherein the master includes a master timer, and wherein the master is configured to generate the data packet and to determine the time stamp value based on the master timer and to enter the time stamp value into the data packet. 
     
     
       14. The bus system according to  claim 13 , wherein the master includes a transceiver circuit connected to a higher-level bus, and wherein the master is configured to synchronize the master timer based on a telegram received via the higher-level bus.